Final answer:
The Bush Doctrine is best characterized by unilateralism and idealism, highlighting the U.S. willingness to act alone and to engage in preemptive actions against perceived security threats.
Step-by-step explanation:
The tenets of the Bush Doctrine of the early 2000s are best described as unilateralism and idealism. This doctrine indicated a willingness to act alone, without the support of international institutions or broad coalitions, and was based on the idea that America should take proactive steps against perceived threats to its security, even if that means preemptive military action. This approach contrasts with multilateralism, where multiple countries work together on foreign policy, and Realpolitik, a theory more focused on practical and material considerations rather than ideological ones.